1. Field of the Invention
The present invention relates generally to a solar lighting reflector apparatus for illuminating the interior of a roofed building, and more particularly, to a solar lighting reflector apparatus having a slatted reflector panel array and an improved solar tracking mechanism for tracking daily movements of the sun.
2. Description of the Prior Art
A variety of measures have been taken to harness the energy of the sun to conserve our limited natural resources. Solar collectors have been used to heat water and other working fluids, and photovoltaic panels have been used to generate electricity from solar energy. In addition, sunlight has been used to illuminate the interiors of buildings. Simple skylights formed in rooftops have long been used to help illuminate buildings. However, such skylights fail to adequately illuminate the interior of a building unless the sun is relatively high in the sky. More recently, skylights supplemented with tracking reflector assemblies have proven to be an economically preferred alternative to electrical lighting in commercial and industrial buildings.
U.S. Pat. No. 4,114,186, entitled "LIGHTING FIXTURE", and issued to the present applicant, discloses a solar lighting fixture which, in one embodiment thereof, includes a telescoping cylindrical light duct including a rotatable upper portion having a pivotally connected reflective lid. Drive motors are provided for rotating the upper portion of the disclosed lighting fixture to follow movements of the sun, as well as to open and close the reflective lid.
U.S. Pat. No. 4,429,952, entitled "TRACKING REFLECTOR ASSEMBLY FOR A SKYLIGHT", and issued to the present applicant, describes a tracking reflector assembly for use in conjunction with a skylight. The reflector assembly includes a ring-shaped base member rotatably supported above the skylight, as well as a reflective panel pivotally coupled to the ring-shaped base member. A horizontal drive motor engages the ring-shaped base member to horizontally rotate the reflective panel, and a vertical drive motor secured to the rear face of the reflective panel operates in conjunction with a pair of rack arms for raising and lowering the reflector. Control circuitry, including various photosensors, is disclosed for selectively operating the horizontal and vertical drive motors to automatically track daily and seasonal movements of the sun. A darkness sensor is also provided for returning the reflector assembly to the east at the end of each day.
The aforementioned U.S. Pat. No. 4,429,952 discloses certain solar tracking circuitry for maintaining the reflector directed toward the sun for tracking daily east-to-west movements of the sun. In particular, this patent discloses the use of a photosensor and an associated shade to control the horizontal drive mechanism. The photosensor is normally shaded when the reflector extends toward the sun, and continued westerly movement of the sun causes direct sunlight to subsequently strike the photosensor to trigger further rotation of the reflector assembly toward the west until the photosensor is again shaded. This patent also discloses a vertical tracking photosensor arrangement wherein a pair of photosensors are positioned behind and on opposing sides of a V-shape shade for sensing changes in the elevation of the sun.
U.S. Pat. No. 4,620,771, entitled "COMBINED SOLAR TRACKING REFLECTOR AND PHOTOVOLTAIC PANEL", also issued to the present applicant, discloses a solar tracking reflector apparatus wherein one or more photovoltaic panels are coupled to the solar lighting reflector apparatus for rotational movement therewith in order to generate electrical power for operating the horizontal and vertical drive motors, as well as the control circuitry related thereto. This patent further discloses a horizontal tracking control arrangement using a pair of photosensors and a shade which prevents sunlight from directly striking one of the two photosensors when the reflector assembly falls behind westerly movements of the sun. A control circuit detects the imbalance between the signals generated by the pair of photosensors in order to advance the reflector assembly further to the west.
U.S. Pat. No. 3,709,583 issued to Pfannkuch et al. discloses a slatted reflector assembly used in conjunction with a skylight wherein the slatted reflectors are mounted in a frame which tracks daily movements of the sun. However, the slatted reflectors disclosed in this patent are formed of prismatic surfaces for reflecting away from the skylight those direct rays of sunlight which strike the slats from a particular range of angles. Accordingly, the reflective slats disclosed by this patent intercept and reflect away, rather than supplement, the direct rays of sunlight which would otherwise enter the skylight dome.
Similarly, U.S. Pat. No. 3,884,414, issued to Baer, discloses a series of louver panels mounted in a frame for use in conjunction with a standard skylight. However, the device disclosed in this patent merely positions the panels to avoid interference with the direct rays of sunlight that would ordinarily strike the skylight, without reflecting additional amounts of sunlight into the skylight.
While the solar lighting reflector apparatus disclosed in the aforementioned U.S. Pat. Nos. 4,429,952 and 4,620,771 have been well received by commercial users, the solar lighting reflector apparatus described in such patents is nonetheless characterized by certain drawbacks. For example, during normal daytime usage, the upper portions of the reflective panel extend four to five feet above the roof and are often visible from the street along which such buildings are located. Apart from detracting from the aesthetic appearance of such buildings, many cities have implemented certain building ordinances prohibiting mechanical equipment installed upon the roof of a commercial building from being visible from the street level. Such building ordinances have occasionally prevented potential commercial users of such solar lighting reflector apparatus from being able to make use thereof.
In addition, the one-piece reflective panels shown in the aforementioned Pat. Nos. 4,429,952 and 4,620,771 can be subjected to rather large wind drag forces on windy days. The presence of unusually high winds requires that the reflective panels be lowered to their horizontal position to avoid damage to the solar lighting reflector apparatus. Accordingly, a mechanical wind sensor and associated electronics are needed to activate the shutdown of such reflective panels under high wind conditions. Little, if any, available daylight can enter the solar lighting reflector apparatus described in such patents during periods when the reflective panel has been lowered due to high wind conditions.
The one-piece reflective panels shown in U.S. Pat. Nos. 4,429,952 and 4,620,771 also fail to distribute reflected light uniformly into the associated skylight under certain conditions. For example, when the sun is at a relatively low angle in the sky, such as during early morning or late afternoon, the reflective panel tends to reflect sunlight primarily upon the rear portion of the skylight, while reflecting very little, if any, sunlight upon the forward portion of the skylight. Similarly, when the sun is relatively high in the sky, as during the noontime portions of summer days, the reflective panel tends to shade the rearmost portion of the skylight while permitting the forwardmost portion of the skylight to receive direct rays of sunlight. When the light entering the skylight is spread thereover in a nonuniform manner, the light transmitted to the interior illuminated space of the building is also typically less uniform.
Additionally, the solar lighting reflector apparatus disclosed in U.S. Pat. Nos. 4,429,952 and 4,620,771 requires a vertical drive motor and related control circuitry for raising the reflective panel at the beginning of each day, lowering the reflective panel at the end of each day, and perhaps raising and lowering the angle of the reflective panel throughout the day to track vertical movements of the sun. One or more geared rack arms cooperate with the vertical drive motor to raise and lower the reflective panel. The required vertical drive motor and related rack arms significantly add to the bulk and complexity of the unit, thereby complicating shipment of the unit prior to installation, as well as complicating maintenance of the unit following installation. Moreover, the electrical power requirements of the vertical drive motor mandate that a relatively large storage battery and relatively large photovoltaic panel be utilized for stand-alone installations, wherein the solar lighting reflector apparatus must generate its own electrical power for operation.
The tracking and control circuitry disclosed in the aforementioned U.S. Pat. Nos. 4,429,952 and 4,620,771 can also present certain disadvantages on occasion. For example, for stand-alone installations wherein the solar lighting reflector apparatus generates all of its own electrical power, the control circuitry is continuously powered and continuously places a drain on the storage battery. During multiple-day periods of extended overcast conditions, the electrical drain placed upon the storage battery by the control circuitry can partially discharge the storage battery, thereby jeopardizing proper operation of the drive motors.
In addition, the control circuitry disclosed in U.S. Pat. Nos. 4,429,952 and 4,620,771 includes a separate darkness sensor for detecting sunset in order to initiate the return of the reflector to an easterly direction for a facing the sunrise on the following morning. The addition of a separate darkness sensor adds to the complexity and cost of such units.
As mentioned above, the control circuitry disclosed in U.S. Pat. Nos. 4,429,952 and 4,620,771 includes photosensitive elements for tracking east-to-west movements of the sun each day to rotate the reflector apparatus about a vertical axis to follow the sun. While such control circuitry typically operates without problems during bright, clear sunny days, problems may arise under cloudy conditions. For example, under cloudy-bright conditions, sunlight may be reflected by or dispersed by the clouds to strike a photodetector that would otherwise have been shaded from direct rays of sunlight. The result is that the control circuitry falsely signals the horizontal drive motor to advance the reflector apparatus in an attempt to once again shade the photodetector. This so-called runaway condition can cause the reflector apparatus to be advanced to its full due-west position even though the sun may still be in the eastern or southern sky.
A further problem which has been discovered with the tracking apparatus and control circuitry disclosed in the two aforementioned patents is the situation wherein the sun is hidden by the clouds during the morning and mid-day hours, but comes out from behind the clouds in the afternoon. During such conditions, the reflector apparatus might never be advanced from its initial due-east position, since the photodetector used to sense east-to-west movement of the sun never receives a sufficient amount of light to trigger the horizontal drive motor. By the time that the sun ultimately comes out from behind the clouds, the sun approaches the reflector apparatus from behind the reflector panel, with the result that the photodetector used to trigger the horizontal drive motor is never illuminated. Thus, although there is enough sunlight in the late afternoon to illuminate the interior of the building, the reflector apparatus remains directed due east.
Accordingly, it is an object of the present invention to provide a solar lighting reflector apparatus incorporating a low preofile reflector assembly for illuminating the interior of a building and being less visible from the street along which such building is located.
It is still another object of the present invention to provide such a solar lighting reflector apparatus which produces significantly reduced wind drag forces under windy conditions, thereby avoiding the need to lower the reflector assembly when relatively high winds are blowing.
It is yet another object of the present invention to provide such a solar lighting reflector apparatus wherein the reflector assembly is easily converted from a compact shipping position to a deployed, operative position.
It is still another object of the present invention to provide such a solar lighting reflector apparatus including a reflector assembly which more uniformly spreads sunlight across an associated skylight dome when the sun is at relatively low elevational angles, as well as when the sun is more directly overhead, as during the noontime portion of summer days.
A further object of the present invention is to provide such a solar lighting reflector apparatus which avoids the need for a vertical drive motor and associated rack arms, which additionally avoids the need for control circuitry used to operate a vertical drive motor, and which further avoids the need for relatively large photovoltaic panels and storage batteries for creating and storing electrical power to operate the vertical drive motor.
A still further object of the present invention is to provide such a solar lighting reflector apparatus including control circuitry which is powered in such a manner as to avoid placing any drain upon a storage battery used to provide power to the horizontal drive motor.
A yet further object of the present invention is to provide such a solar lighting reflector apparatus and related control circuitry wherein a separate darkness sensor is not required to trigger the return of the apparatus to its due east position at the end of each day.
An additional object of the present invention is to provide such a solar lighting reflector apparatus including solar tracking control circuitry which inhibits the aforementioned "runaway" situation brought about by cloudy-bright conditions during which the horizontal drive motor is continuously operated in a futile attempt to find the position of the sun.
A further object of the present invention is to provide such a solar lighting reflector apparatus having solar tracking control circuitry adapted to seek out the position of the sun once the sun comes out from behind the clouds after extended hours of overcast conditions.
These and other objects of the present invention will become more apparent to those skilled in the art as the description thereof proceeds.